Hey everyone, I have spent an hour debugging and still cannot find where’s the problem.
For 3.1 - The Identity Block, I am sure I use
Add()([X, X_shortcut]) for the adding shortcut to X
I am sure I follow the instructions and set different kernel size 1 and f , and 1 and padding …
but still get this error.
this is 2025 version of notebook
so there is not “training” parameter already
One common error is not using the correct input to the “shortcut” step. The instructions mention it, but aren’t really that expressive. It’s the diagram that really is the best description of what is intended here.
Thanks @paulinpaloalto . I just go for a break and restart the notebook twice and it suddenly works. I don’t change anything…
but still thank you for your reply.
Interesting. That probably means that your code was right to begin with, but you had not re-executed the cell after you fixed the last bug in it. If you type new code in a function and then just call the function again, it runs the old code. You have to actually click “Shift-Enter” on the modified cell in order to get the new code “compiled” (well, “interpreted” really) into the runtime image. Or doing the classic:
Kernel -> Restart and Clear Output
Save
Cell -> Run All
will get things back in sync so that WYSIWYG. 
You can easily demonstrate this behavior to yourself:
Take a function that already works and purposely break it. E.g. multiply the return value by 2. Then call the function again. The test still passes, right? Now click “Shift-Enter” on the newly broken cell and then run the test cell that calls the function again. Kaboom! 